The present invention is generally directed to motor assemblies. In particular, the present invention is directed to motor assemblies with improved lamination design that results in improved electrical performance and improved thermal management capability.
Electrical motors are used to operate any number of household appliancesxe2x80x94such as mixers, vacuums, compressors and the likexe2x80x94and industrial devices. In their most basic form, electricity is supplied to a motor assembly to rotate a shaft which in turn operates the equipment directly or through some type of gearing mechanism.
A motor assembly includes an armature from which the shaft axially extends and which is mounted within a field or a brace. Both the armature and field assemblies are separately wound with an insulated wire to facilitate the generation of a magnetic field. Application of an electric current energizes the windings and causes the armature to rotate within the field which in turn rotates the shaft. As is well known, the armature and the field are made of steel laminations that are stacked upon one another to a desired length. This stacking reduces the extraneous eddy currents that would otherwise exist for a solid core armature or a solid core field and also improves the overall motor operating efficiency.
Moreover, efficient operation of the motor is dependent upon many variables of motor design, including, but not limited to, wire resistance, lamination material properties, the size, shape and thickness of the laminations and so on.
In previous motor designs it was believed that a rounded field lamination configuration, as shown in FIG. 1, was adequate for fractional horsepower motors used for cleaning appliances and the like. However, use of these motors with a rounded field lamination configuration is believed to be inefficient in design and in particular in the varying amounts of xe2x80x9cback ironxe2x80x9d used in the field assembly and the armature assembly. Those skilled in the art will appreciate that back iron refers to the amount of magnetic materialxe2x80x94the steel laminationxe2x80x94used in a motor assembly. These designs are limited in that they heat up rapidly due to the lack of airflow once the windings are in place on both the field assembly and the armature assembly. It is believed that little if any consideration has been given to these features inasmuch as the current motor design used in these fractional horsepower devices has remained relatively unchanged over the past 25 years. Therefore, it is believed that there is a need in the art for a motor assembly having improved flux density properties. It is further believed that by properly sizing the back iron, improved air flow and motor performance can be obtained.
The objects of the present invention are attained by a motor assembly having improved flux density comprising: a field assembly; an armature assembly rotatably received in said field assembly, said field assembly including a plurality of like laminations stacked upon each other, each said field lamination comprising; a pair of substantially parallel bracket sides; a pair of substantially parallel yoke sides which are substantially perpendicular to said pair of bracket sides; corner pieces connecting said yoke sides to said bracket sides, wherein said corner pieces are angularly directed between about 40xc2x0 to about 50xc2x0 with respect to said yoke sides and said bracket sides; a yoke extending inwardly from each said yoke side to form an armature opening therebetween for rotatably receiving said armature assembly, wherein said bracket sides, said yoke sides and said corner pieces forming airflow areas therein; and wherein said bracket sides, said yoke sides, except at said yokes, and said corners all have substantially the same width dimension, such that said yoke sides, said bracket sides and said corners have substantially equivalent average field flux density ratios.
These and other objects of the present invention, as well as the advantages thereof over existing prior art forms, which will become apparent from the description to follow, are accomplished by the improvements hereinafter described and claimed.